checklab – A patch for the label-checking code

Patch for the ker­nel la­bel-check­ing code at end doc­u­ment, to
pro­duce an ex­plicit mes­sage (al­beit a some­what in­scrutable one)
for each la­bel that it thinks has changed (and how it has
changed). This is use­ful if you are de­vel­op­ing macros that use
la­bels in odd ways.

One of a se­ries of frag­ments
de­signed for use by pack­age writ­ers and oth­ers.